The most straightforward secret to access. In the purple forest, there is a body of water you can cross on the top right screen. You can then burn the trees blocking access to the screen above to get your first hint.
Now what in the world does this even mean, you're probably wondering. Sight must be referring to eyesight, right? Where have we seen something that this could be referring to?
Of course! While the sane may not notice it, this screen in the cayeen does bare some resemblance to a face. But what does the cave give you?
A key! At this point, most observant players probably already know where they can use this.
Inside this cave will be a puzzle. Upon completion, you will be given the Bait.
But where can we use the bait?
In the area above the Cayeen, bomb this spot:
Inside will be a hungry Goriya, feed him the bait and you'll be given access to the next room which holds the super bombs
Now where can super bombs be used? Exclusively on these purple rocks
There's a spot right next to the cave where you obtain the super bombs that has another optional purple rock. If you blow it up, you'll gain access to a shop that sells more super bombs if you want any later for whatever reason.
That said, now that you have access to the first secret dungeon, you'll be able to access the second after completing it.
Beneath this room in Eddy's Way is a room that requires the longshot to progress.
Longshot across, step in the warp, and you'll find the second secret dungeon.